The effect of neonatal undernutrition on norepinephrine (NE), dopamine (DA), and serotonin (SHT) biochemistry will be studied in the rat. Undernutrition will be induced (1) preweaning by feeding a low protein diet to lactating females and (2) postweaning by feeding a low diet for 3 weeks. Development of central neurochemical systems will be monitored by study of regional development of brain NE, DA plus 5HT, tyrosine hydroxylase (TH), dopamine-B-hydroxylase (DBH) and tryptophan hydroxylase. Synthesis of NE, DA from tyrosine and 5HT from tryptophan will also be assessed. Parallel studies (re catecholomines) will be carried out in the peripheral neurons system: adrenal gland, superior cervical ganglia, and mesenteric artery. All biochemical determinations will be carried out from birth to adult, during periods of undernutrition as well as after period of nutritionally rehabilitation. The adult response to stress (foot shock, swimming) will be studied by assessing rate of NE, DA and 5HT synthesis. These studies should elucidate some of the neuronal mechanisms underlying the behavioral aberrations observed in adult animals nutritionally deprived during early growth and development.